The present invention relates to the detection and characterization of medical pathologies in human and animal bodies. More particularly, the present invention relates to the detection and identification of cancer in organs or tissues.
There are no available systems today, for medical or non-medical applications, to detect and characterize distinct features within an object under study, such as cancerous lesions and tumors in a human body. Presently, only imaging systems are available, such as imaging systems based on x-ray, mammography, computed tomographic (CT) scans, or magnetic resonance imaging (MRI). All of these imaging systems simply provide images of pathologies within a human body; they do not characterize any features.
In addition, each of these imaging technologies has significant drawbacks. For example, x-rays, mammography, and CT scans all use ionizing radiation and therefore present certain health risks to a patient, such as cell mutations. Also, both CT scans and MRI involve procedures that are relatively expensive, which hampers their widespread use. Moreover, both MRI and CT scans require the expertise of highly trained personnel for extended periods of time to operate the devices and to interpret the results. Furthermore, each of these imaging technologies requires that the patient lie still, sometimes for an extended period of time. This restriction on movement may not only inconvenience the patient, but also discards information that could potentially be discovered from the movement of tissues within the patient. As to mammography, it is particularly uncomfortable for the patient since it requires that the breast be compressed to allow more uniform tissue density, better x-ray penetration, and tissue stabilization. More importantly, methods such as mammography rely on two-dimensional images, thus disguising three-dimensional structure information which can be critical for diagnosis.
As an alternative to the above-mentioned imaging technologies, the medical community has looked to ultrasound for providing a safe, low-cost, high-resolution imaging tool. However, conventional ultrasound (ultrasonic B scanning) has certain limitations. In conventional ultrasound analysis, a small array of less than approximately 1000 elements is moved by hand in contact with the object under study. In fact, most current ultrasound arrays have only 256 elements. The array sends out waves that reflect from tissues back to the same array. Trained technicians and physicians are needed to conduct the ultrasound imaging procedure and to interpret the results. This reliance solely on the reflected waves results in two major drawbacks. First, ultrasonic B scans do not provide information on the properties of the materials themselves; rather, they provide information on the reflectivity of the boundaries between different types of materials. Second, the array is incapable of capturing radiation except that which is reflected back to the hand-held sensing array. Considerable information exists, however, in the transmitted waves, which is not captured or used in conventional ultrasonic B scans.
There is thus a need for an apparatus and method that provides detection and characterization of medical pathologies in a human body. More generally, there exists a need to detect and characterize distinct features within an object under study.
The present invention provides construction and use of multidimensional field renderings for high-resolution detection and characterization of distinct features within a three-dimensional object. More particularly, the invention provides construction of such multidimensional field renderings for high-resolution detection and identification of medical pathologies in human and animal bodies, especially high-resolution detection and identification of cancer in organs or tissues. The present invention also provides detection and characterization of other medical pathologies including pathologies of musculoskeletal systems, digestive systems, and the alimentary canal, in addition to atherosclerosis, arteriosclerosis, atherosclerotic heart disease, myocardial infarction, trauma to arterial or veinal walls, and cardiopulmonary disorders.
The present invention provides construction of a multidimensional field rendering that describes the physical details of any three-dimensional object under study. By correlating the information contained in such a multidimensional field with information regarding known details of general objects under study by using a trained evaluation system, the present invention provides detection and characterization of the structures that exist in the object under study. For example, the present invention provides a system based on ultrasound which, when it is used to observe a human breast, correlates a catalog of known morphologies and acoustic characteristics of tissue types that are known to exist in breast tissue with the multidimensional field derivation of physical properties; then the system of the present invention detects and characterizes various tissues including fibroadenoma, fat, fibroglandular tissue, and benign versus malignant lesions or tumors.
The present invention provides a method and apparatus that allows for the detection and characterization of features within an object under study. The invention uses an array of radiation sources and an array of radiation detectors to collect scattered radiation regarding the object under study. In one preferred embodiment, the source array and detector array are configured as a single integrated unit. In another preferred embodiment, the radiation sources and detectors are the same physical devices; they operate in one time period as radiation emitters and in another time period as detectors. In yet another preferred embodiment of the invention, the arrays comprise large numbers of sources and detectors, preferably with more than 5000 detectors. With a sufficient number of such sources and detectors, the present invention provides for construction of a three-dimensional rendering of numerous physical quantities to describe the object and therefrom derive interpretations. The radiation sources emit radiation of a specific waveform, either within a predetermined frequency range or at a predetermined frequency, which is propagated within the object under study and subsequently scattered by features within the object under study. Generalized scattering includes reflection (backscattering), transmission (forward scattering), and diffraction, which may occur in any or all directions from the features within the object under study. All these types of secondary waves constitute the wave signal returned from the object under study.
In a preferred embodiment, the radiation sources and detectors cover a large solid angle, thereby substantially enclosing the object under study. As a result, a large fraction of all these types of secondary waves are detected by the radiation detectors. The resolution depends on the product of the number of sources and the number of detectors, which defines the number of resolution elements into which the volume occupied by the object under study may be divided.
In a preferred embodiment of the invention, the radiation is ultrasound radiation, although the invention generally encompasses the use of any radiation, including electromagnetic and acoustic radiation. In more specific embodiments of the invention, the object under study is tissue or an organ, or other part of an animal body such as the human body. By using a sufficiently large number of detectors and sources, a high resolution multidimensional field is provided in accordance with the present invention. In another embodiment of the present invention, the sources are modulated to have different phases, which permits focusing or scanning of the radiation.
In accordance with another embodiment of the present invention, the radiation is sufficiently focused and is used to destroy features within the object, such as cancerous lesions within human or animal tissue.
In accordance with the present invention, the data collected by the radiation detectors are then used to construct a rendering of a multidimensional field, represented herein as [r,t:"THgr"(r,t)], that represents physical characteristics of the object under study. The vector r represents the position coordinate of a particular volume element (xe2x80x9cvoxelxe2x80x9d); xe2x80x9ctxe2x80x9d is the time"" and xe2x80x9c"THgr"xe2x80x9d is a list of the physical parameters associated with the field at that voxel. In general, the field and each physical parameter are both spatially and time dependent. The multidimensional field comprises estimates of the values for this set of parameters that individually represent physical characteristics of the object under study. These parameter values, taken together, characterize the properties of features within the object under study. In the case of medical applications, this characterization results in the identification of focal regions, their probability of pathology, such as malignancy, and associated probabilities of frequency distribution and error rate.
As an illustration, consider those embodiments of the invention where the radiation is ultrasound radiation and the object under study is a human organ. In this illustration, [r,t:"THgr"(r,t)] may describe, for example, the sound speed, sound absorption, tissue pressure, density, shear modulus, elasticity, etc., of the organ as functions of frequency. The field values are stored electronically into a computer-readable medium, such as a floppy disk, random access memory, or hard memory disk. This allows subsequent processing of the stored field values.
In accordance with a preferred embodiment of the present invention, the construction of the rendering of the multidimensional field [r,t:"THgr"(r,t)] from the detected data, which comprise elements from a description of the waveform of the detected radiation at the location of each detector, is accomplished with an optimal signal processing technique.
In one embodiment of the invention, this is accomplished with matched-field processing, in which the field rendering is constructed so as to produce model detector data that matches the actual detector data, and which may be achieved through an iterative technique. In this iterative technique, the shape of the object under study is first estimated. This can be achieved in a number of different ways, using existing techniques, such as using the transmission-only radiation detected and developing the initial estimate with conventional computer tomographic techniques. In the embodiment where the object under study is human or animal tissue, organ, or other body part, this initial estimate is referred to as an xe2x80x9canatomicxe2x80x9d construction.
An initial estimate of the multidimensional field est[r,t:"THgr"(r,t)] is then calculated by injecting physiological data to produce a xe2x80x9cphysiologicalxe2x80x9d construction. This proceeds by using a pattern-recognition algorithm, such as an expert system, to analyze the morphological features of the anatomic construction and thereby to assign an initial, nominal estimate of the multidimensional field. This nominal estimate is based solely on average values that structures in the object are expected to have based on their morphologically based identification by the pattern-recognition algorithm. The pattern-recognition algorithm achieves this initial assignment by comparing the morphological features of the anatomic construction with a database of stored morphological features, such as elongation, flatness, jaggedness, etc.
At this point, the physical characteristics of the object contained in the estimated field est[r,t:"THgr"(r,t)] are input into a wave-propagation code, together with the information concerning the characteristics of the radiation that was initially generated. Such a wave-propagation code can be used to generate the waveform of the radiation that would be expected at the locations of the detectors based on this information. Such wave-propagation codes can be rather complex, but exist in the prior art. Once these signal data have been generated based on the estimated field, they are compared with the actual signal data that was received by the detectors. If the difference between the two sets of signal data is at the level expected for noise in the system, then the estimated field is taken to be the actual constructed field rendering, i.e. [r,t:"THgr"(r,t)]est [r,t:"THgr"(r,t)].
If, however, the comparison with the actual signal data shows that the difference between the signals generated by the estimated field and the actual signals is greater than the expected noise in the system, then a correction to the estimated field is calculated. This correction is determined by using a wave-propagation code to generate a refinement field [r,t:"THgr"(r,t)] from the difference in actual signals and signals that would be produced by the estimated multidimensional field. This refinement field is then used to modify (e.g., by adding to) the estimated field to produce a new estimated field, which is then used to calculate a new set of detected signals. The process is iterated until the set of signals generated from the estimated multidimensional field est[r,t:"THgr"(r,t)] converge to a converged multidimensional field [r,t:"THgr"(r,t)], which generates waveform signals that are within the noise level of the actual set of detected signals.
Once the multidimensional field [r,t:"THgr"(r,t)] has been calculated, it is interpreted so as to characterize the object under study. This is done, for example, with the use of an expert system, neural net, or other trained evaluation system that has been taught to take the values calculated for [r,t:"THgr"(r,t)] at every voxel and to reach a determination of what the identified features in the object under study are. The specific features of the multidimensional field that are relevant for the interpretation method executed by the trained evaluation system depend both on what the object under study is and on what is to be learned about the object.
For example, in the embodiment of the invention where human or animal tissue or an organ is studied with ultrasonic radiation and the goal is to identify diagnostic parameters suggestive of the existence of cancer, there are at least seven identification methods that are used to extract information from the multidimensional field so as to allow the trained evaluation system to draw such interpretations.
In a first identification method, the converged multidimensional field will contain the sound speed and sound absorption of the tissue or organ at every voxel. The trained evaluation system will then classify the type of tissue present at every voxel based on this information, and will identify cancerous tissue based on these particular physical properties.
In a second identification method, a Hough transformation of the multidimensional field is used to identify closed volumes in the tissue, which are indicative of the existence of neoplasms.
In a third identification method, the existence of angiogenesis and other anomalies of the circulatory system are identified by examining three-dimensional blood flow with the Doppler effect.
In a fourth identification method, the tissue pressure is extracted from the multidimensional field and correlated with the localization of an enclosed volume, as well as any distinct results from the other identification methods.
In a fifth identification method, the Doppler effect is used to analyze the effects of external vibrations on the tissue, which produce characteristic results in the multidimensional field to allow the identification of tissue shear modulus. In a related method, microcalcifications and tissue elasticity, which are also suggestive of cancer, produce a characteristic Doppler signature.
In a sixth identification method, information regarding the electrical impedance of tissue is extracted from the multidimensional field. This information is related to the existence of tumors.
In a seventh identification method, the multidimensional field rendering is constructed at two different times and compared either to study changes over time in the tissue or to allow the use of interferometric techniques to improve the resolution.
The actual identification of medical pathologies such as cancerous tissue preferably uses more than one of these identification methods in conjunction. With the use of multiple identification methods, the reliability of the evaluation is improved. In this way, for example, a human breast may be examined with ultrasonic radiation to identify cancerous tissue at the desired resolution. In other embodiments, the invention is used to identify cancer in other organs, such as the prostate, colon, lung, etc.
It is thus an object of the invention to produce an apparatus and method for sensing the spatial, or spatial and temporal, properties and determining the physical and/or biological nature of materials in a substantially enclosed volume.
It is another object of the invention to perform sensing operations that uniquely identify physical properties in contiguous, highly resolved volume elements throughout the sensed media.
It is yet another object of the invention to provide a disease-detection system specifically designed to find small, subtle indicators of early pathology, including cancer, vascular disease, etc.
It is still a further object of the invention to produce a class of physics-based diagnostic devices that probe the subject environment, observe the response of the contents to the probing disturbance, and then diagnose the implications of the measured data.
An advantage of the invention is that it provides detection and identification of tissue anomalies where the object under study is animal or human tissue or an organ. In particular, the invention detects and identifies cancerous tissue in animal and human organs. The invention also provides detection and identification of other medical pathologies in systems including cardiovascular, musculoskeletal, or digestive systems. The disease states that may be characterized include trauma, infection, neoplasms, and disorders of various biochemical pathways.
It is a further advantage of the invention that it provides construction of the multidimensional field rendering in three spatial dimensions by using of all scattered radiation, which includes radiation reflected, transmitted or diffracted by the object under study or by features within the object under study.
An additional advantage of the invention is that it permits the complete use of Doppler shifted data, since there is no limitation to Doppler shifts that lie in a single plane of examination.
Other objects and advantages may occur to those of skill in the art after reading the detailed disclosure and figures. The invention is not limited to those objects and advantages recited above, but encompasses all objects and advantages that would occur to those of skill in the art in light of the disclosure.